Optical coherence tomography (OCT) is an emerging technique for in-vivo microscopy which obtains micron-scale cross-sectional images of subsurface structure in biological tissues. While conventional OCT measures the depth-resolved reflectivity profile of backscattered light, polarization-sensitive OCT (PS-OCT) systems have been developed to add the capability of controlling the polarization state of light incident upon the sample and measuring the reflectivity of light returning in particular polarization states. See, for example, M. R. Hee, D. Huang, E. A. Swanson and J. G Fujimoto, J. Opt. Soc. Am. B 9, 903 (1992); and J. F. de Boer, T. E. Milner, M. J. C. van Gemert and J. S. Nelson, Opt. Lett. 22, 934 (1997), the entire disclosures of which hereby are incorporated by reference. Such selectivity allows for the measurement of birefringence and/or dichroism. Prior studies in biological samples have found the effects of dichroism to be minimal in skin and muscle tissue, and have focused on measurement of retardation due to birefringence for contrasting different types of tissue and assessing the severity of burns. See, for example, C. E. Saxer, J. F. de Boer, B. H. Park, Y. Zhao, Z. Chen and J. S. Nelson, Opt. Lett. 25, 1355 (2000); J. F. de Boer, T. E. Milner and J. S. Nelson, Opt. Lett. 24, 300 (1999); and K. Schoenenberger, B. W. Colston, D. J. Maitland, L. B. Da Silva and M. J. Everett, Appl. Opt. 37 6026 (1998), the entire disclosures of which hereby are incorporated by reference. PS-OCT systems also avoid polarization artifacts which occur in conventional OCT images of birefringent samples. See, for example, M. J. Everett, K. Schoenenberger, B. W. Colston and L. B. Da Silva, Opt. Lett. 23, 228 (1998), the entire disclosure of which hereby is incorporated by reference.
Most conventional OCT systems use non-polarization-maintaining (PM) single-mode fiber interconnections because they are inexpensive, allow for easy alignment and handling, and enable flexible sample arm designs which are important for in vivo measurements such as surgical and endoscopic applications. Single-mode optical fiber, however, exhibits undesirable static and dynamic polarization effects due to fiber imperfections, fiber bending, and temperature fluctuations. Most prior PS-OCT systems have been implemented in bulk optics due to the difficulty of maintaining predictable polarization in conventional fibers, and have employed dual orthogonally polarized detection channels. Recently, a conventional-fiber based PS-OCT system has been reported which depends upon the assumption that the non-PM fiber is lossless. See C. E. Saxer, J. F. de Boer, B. H. Park, Y. Zhao, Z. Chen and J. S. Nelson, Opt. Lett. 25, 1355 (2000), which also is identified above.